Английская Википедия:Engadine Line

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Версия от 19:34, 3 марта 2024; EducationBot (обсуждение | вклад) (Новая страница: «{{Английская Википедия/Панель перехода}} {{Use dmy dates|date=December 2023}} {{good article}} {{short description|Strike-slip Fault in Switzerland, Italy and Austria}} The '''Engadine Line''' is an over {{convert|50|km|-1}} long strike-slip fault in the Swiss canton of Graubünden, which extends into Italy and Austria. It runs along the Engadine Valley (which formed on the fault) and the Bregaglia V...»)
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Шаблон:Use dmy dates Шаблон:Good article Шаблон:Short description The Engadine Line is an over Шаблон:Convert long strike-slip fault in the Swiss canton of Graubünden, which extends into Italy and Austria. It runs along the Engadine Valley (which formed on the fault) and the Bregaglia Valley and offsets Austroalpine and Penninic units in a sinistral direction. The western end of the fault appears to peter out into ductile deformation in the Bregaglia Valley or continues as the Gruf Line to the southwest; the eastern end is buried by the Ötztal tectonic block and may continue as the "Inntal fault", "Isar fault" or "Loisach fault".

Total offset along the Engadine Line is about Шаблон:Convert, decreasing southwest. It began in the Oligocene, but there is evidence of recent neotectonic activity, which resulted in the collapse of the Maloja Pass area at the beginning of the Holocene. Seismic activity occurs along the Engadine Line, and springs and carbon dioxide exhalations in the Engadine are linked to the fault.

Geology

Файл:Schema tettonico delle Alpi.jpg
Tectonic map of the Alps, the Engadine Line is marked with "L.E."

The Engadine Line is an over Шаблон:Convert long[1] northeast-trending fault in southeastern Switzerland.Шаблон:Sfn It was originally discovered in 1896 and named "Engadiner Spalte".Шаблон:Sfn It is a steeply dippingШаблон:Sfn left-lateral strike-slip faultШаблон:Sfn that cuts to a depth of Шаблон:Convert.Шаблон:Sfn The total slip on the Engadine Line decreases from Шаблон:Convert in the Lower Engadine to Шаблон:Convert in the Upper EngadineШаблон:Sfn and Шаблон:Convert at Sils, Maloja.Шаблон:Sfn The towns of Bever, Maloja, Nauders, S-chanf, Samedan, Sils, St. Moritz, Vicosoprano and Zernez are located along the Engadine Line,Шаблон:Sfn as is the Albigna Dam.[2]

The fault trace is generally not recognizable on the surface, as it is buried beneath alluvium; the only outcrops are found at MalojaШаблон:Sfn and at Stragliavita close to Zernez.Шаблон:Sfn Parts of the Engadine Line were already recognized by 1914, but it was only in 1977 that they were identified as belonging to a single fault zone,Шаблон:Sfn reportedly after a suggestion by a Chinese geologist.[3] Sometimes the names "Nassereith-Silz fault" and "Scuols-Vils fault" are used for the Engadine Line,[4] which was originally also known as Шаблон:Lang.Шаблон:Sfn

The Engadine Line deforms the Austroalpine and Penninic nappesШаблон:Sfn and also appears in magnetic anomaly maps.[5] It is responsible for the geologic differences between Graubünden north and south of the Engadine.[3] The Engadine Line is sometimes considered to be a branch of the Periadriatic Fault System.[6] The movement on the Engadine Line is part of a larger tectonic process in the Alps, whereby the mountain range is compressed in north-south direction and is thus squeezed upwards and eastwards.Шаблон:Sfn Of the numerous fault zones in the Eastern Alps, the Engadine Line and its northeastern extensions are the longest.Шаблон:Sfn

Evidence for a vertical component in fault motion and its interpretation is conflicting;Шаблон:Sfn the block southeast of the fault has a down-to-the-east componentШаблон:Sfn with normal slip in the northeastern sector of the Engadine LineШаблон:Sfn that may be part of east-west extension in the Alps,[7] while the sector in the Bregaglia Valley features an uplifting northwestern blockШаблон:Sfn with reverse slipШаблон:Sfn that may be a recent change in fault motion.Шаблон:Sfn Vertical offset on the Engadine Line appears to have opposite direction east and west of Samedan–St. MoritzШаблон:Sfn and has been interpreted as a rotational movement of tectonic blocks.Шаблон:Sfn The Churer uplift influenced the western side of the Engadine Line and generated eastward tilting.[8]

Geomorphology

Файл:Karte Kreis Oberengadin 2016.png
Map showing some toponyms associated with the Engadine Line

In the Lower Engadine, the Engadine Line delimits the Silvretta covers and the Engadine Window from the Ötztal Alps block,Шаблон:Sfn which appears to bury the Engadine Line in part.Шаблон:Sfn The movement along the Engadine Line may have generated the Engadine Window by exposing Penninic rock units.Шаблон:Sfn The Schlining Thrust, which separates the Austroalpine Ötztal unit in the east from the Sesvenna-Campo-Silvretta units in the west,Шаблон:Sfn joins the Engadine Line in Austria. On its eastern end the Engadine Line may reach into the Northern Calcareous Alps[9] and can be traced as far as the town of Imst in Austria;[10] it may reach as far as Innsbruck.Шаблон:Sfn The Inntal fault is probably the northeastern continuation of the Engadine LineШаблон:Sfn and has a maximum offset of Шаблон:Convert, reaching the Molasse basin.Шаблон:Sfn The Loisach[11] and the Isar faults are other candidate prolongations of the Engadine Line;Шаблон:Sfn alternatively, the former has been interpreted as a parallel fault that splits up in the Wetterstein Mountains.Шаблон:Sfn Later movements in the Ötztal Alps area may have overprinted the trace of the Engadine Line there.Шаблон:Sfn It is conjugated with dextral strike-slip faults in the Northern Calcareous Alps.[12]

The Inn River valley formed along the Engadine Line.[6]Шаблон:Sfn There, the fault runs e.g between the villages La Punt and St. Moritz.[10] In the Samedan area, geologic research has found evidence of releasing bends and restraining bends associated with Miocene movement along the Engadine Line,[13] as well as of normal faults linked to the Engadine Line.[14] Offsets in road cuts at Seraplana have been associated with the fault.Шаблон:Sfn At Zernez the river departs the Engadine Line before returning at Scuol.Шаблон:Sfn The Engadine Line might form the northwestern border of the Scarl-Campo rock units.[15] The combined effects of glacial erosion and slip along the Engadine Line generated the Lej da Segl, Lej da Silvaplauna, Lej da Champfèr and Lej da San Murezzan lakes which are traversed by the Inn River.[8] The fault cuts across the Isola delta of Lake Sils.Шаблон:Sfn

In the Upper Engadine and the Maloja Pass area the Engadine Line is represented by Шаблон:Convert long northeast-trending and Шаблон:Convert long east-west trending fault segments which form scarps. Depressions located between the fault traces are occupied by lakes such as Silsersee, Silvaplanersee and St. Moritzsee, which do not appear to be moraine-dammedШаблон:Sfn and may have been formed by the activity of the Engadine Line.[6] Subaqueous ridges in Lake Sils are linked to the fault.Шаблон:Sfn Close to the Maloja Pass the Engadine Line forms a single fault.Шаблон:Sfn In the Forno Valley the fault crops out in the form of polished surfaces, scarps and striations along with fault gouge.Шаблон:Sfn The course of the Orlegna River is diverted by a shutter ridge at the intersection with the Engadine Line.Шаблон:Sfn There, the Engadine Line runs along the southern side of the Inn and Bregaglia Valleys and is accompanied by deep-seated mass failures; eventually it disappears under sedimentsШаблон:Sfn close to Promontogno.Шаблон:Sfn As with the Inn Valley, the Bregaglia Valley is the surface expression of the Engadine Line.Шаблон:Sfn

The Engadine Line continues as the "Gruf Line", which runs along the southern side of the valley, accompanied by deep-seated mass failuresШаблон:Sfn which obscure the surface presentation of the Gruf Line,Шаблон:Sfn and crosses into Italian territory.Шаблон:Sfn The Gruf Line appears to be based in deeper, more ductile crustal domains than the Engadine Line, and it is possible that part of the offset is taken up by ductile stress along the Bregaglia Valley.Шаблон:Sfn Alternative interpretations see the Gruf Line as a mylonite zone,Шаблон:Sfn discuss a "Bergell Fault" that constitutes a southwestern expression of the Engadine Line and the root of the Bregaglia,Шаблон:Sfn identify another lineament between Maloja and Chiavenna, or prolong the Engadine Line to Chiavenna and even farther.Шаблон:Sfn The Gruf line separates the Gruf migmatites from the Chiavenna ophiolites and the Tambo nappe.Шаблон:Sfn It and the Gruf Line accommodate the exhumation of the Bergell pluton,Шаблон:SfnШаблон:Sfn which was tilted to the east between the Engadine Line and the Periadriatic Line.Шаблон:Sfn

A transition from brittle faulting on the Engadine Line to ductile deformation in the western Bregaglia Valley might explain why the Engadine Line does not appear to continue there.Шаблон:Sfn Slope instability that causes frequent landslides[16] and deformation in rock formations of the Bregaglia Valley may related to activity of the Engadine Line.Шаблон:Sfn Structural lineaments related to the Engadine Line can be traced as far as the Valle San Giacomo west of the Bregaglia.[17]

Geologic history

Шаблон:Geology of the Alps

Movement along the Engadine Line commenced during or before the late OligoceneШаблон:Sfn but post-dates the cooling of the Bergell pluton 28 million years ago.Шаблон:Sfn Movement took place during the OligoceneШаблон:Sfn before probably ceasing during the Miocene[18] and has been attributed to the so-called "Turba phase" of extensional development of the Alps.[19] The movement along the Engadine Line and Inntal faults influenced the course of the Inn River,Шаблон:SfnШаблон:Sfn allowed its watershed to expand southwestwards,Шаблон:Sfn and altered drainages during the Sarmatian.Шаблон:Sfn The weak rock along the fault was easily eroded by glaciers, and glacial erosion eventually formed the Engadine valley along the fault.Шаблон:Sfn

Neotectonics

There is very little information on the recent activity of the Engadine Line.Шаблон:Sfn Detecting faults in the Alps is difficult, as glacial and fluvial erosion as well as gravitational processes and landslides quickly erase evidence of tectonic processes.Шаблон:Sfn Earthquakes are often poorly documented in the thinly populated Alps; they tend to be weak and often cannot be linked to specific faults.Шаблон:Sfn

There are only few indications of recent activity, and it is not agreed upon that it was active during the Upper Pleistocene-Holocene,Шаблон:Sfn although evidence of Quaternary movement is widely found.Шаблон:Sfn The Engadine Line and other lineaments delimit a fast uplifting area of the Central Alps.[20] In the Val Laschadura, close to Zernez, post-glacial faulting is recorded,Шаблон:Sfn[21] and recent vertical offsets of more than Шаблон:Convert are recorded from fluvial sands close to Piz Mundin.[22] Trees that drowned between 650-700 AD in Lake Sils, and around 1000 AD as well as at the beginning of the 14th century in Lake Silvaplana may indicate lake level changes or ground subsidence triggered by tectonic activity on the Engadine Line.Шаблон:Sfn A large earthquake in the Alps during the 6th century left traces in the Engadine lakes, but the Engadine Line is unlikely to have been its source.[23] Traces of multiple glaciations are preserved in the Forno Valley. Deposits left by the most recent glaciation are unaffected by tectonic activity at the Engadine Line,Шаблон:Sfn but the Orlegna River has not yet recovered from the impact of faulting, implying that movement along the Engadine Line there took place before 14,500 years ago but in the Late Pleistocene. Fault scarps in the Inn Valley associated with the Engadine Line have been degraded by glaciation.Шаблон:Sfn On the other hand, sackungen in the Bregaglia Valley which post-date the last glacial maximum have been linked to tectonic activity on the Gruf Line,Шаблон:Sfn which otherwise shows no evidence of Quaternary activity.Шаблон:Sfn The deformation in the western Inn Valley-Bregaglia Valley may be of gravitational origin, however,Шаблон:Sfn although earthquakes on the Engadine Line may have triggered their movement.Шаблон:Sfn

The "beheading" of the Inn Valley at Maloja Pass, which took place between 29,400–14,500 years before present,Шаблон:Sfn is one of the major geologic events in the Quaternary of this sector of the Alps. Three valleys that formerly presumably fed the Inn Glacier were redirected into the Bregaglia Valley by a large collapse that caused the "beheading". Tectonic stresses exercised by movements along the Engadine Line may have caused the collapse,Шаблон:Sfn which left a steep escarpment at Maloja Pass and a large elevation difference between the Inn and Bregaglia valleys.Шаблон:Sfn

Seismicity

It is possible, but unproven, that the Engadine Line may generate earthquakes.[24] Minor seismic activity occurs in the EngadineШаблон:Sfn defining the "Engadine seismogenic zone",[25] which in the 1980 seismic hazard map of Switzerland was considered an area of significant seismic hazard.[26] It appears to relate, in part, to northeast-southwest trending structuresШаблон:Sfn such as the Engadine Line.[25][27] Earthquakes have been localized to the Engadine Line, but they are not intense, and seismicity disappears into the Inn Valley, where the Engadine Line fault continues.Шаблон:Sfn It decreases southwestwards away from the central and eastern Engadine.Шаблон:Sfn Seismic activity in the Venosta Valley may be related to the intersection between the Engadine Line and a north-south trending fault.Шаблон:Sfn

Turbidites in Lake Como and Lake Sils, dated to have occurred in AD 700, may relate to Engadine earthquakes.[28] In the Ötz River valley in Austria, the Engadine Line and the Inntal fault have been related to increased earthquake activity, which may explain the occurrence of frequent landslides in the area.[29] Research published in 1979 indicated that earthquakes on the Engadine Line might reach a maximum magnitude of Шаблон:M 5.5[4] or 6.9 with a break length of Шаблон:Convert.[30]

Exhalations and springs

Hydrothermal activity has been associated with recent activity on the Engadine Line.Шаблон:Sfn In the Scuol-Tarasp area, mineral water and carbon dioxide rise to the surface (the latter forming mofettes)Шаблон:Sfn along the Engadine Line and its intersection with more local geologic lineaments.Шаблон:SfnШаблон:Sfn The waters most likely form along the plane of the fault.Шаблон:Sfn

References

Шаблон:Reflist

Sources

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Разное

  1. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Wexsteen1988 не указан текст
  2. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Gimenes2006 не указан текст
  3. ↑ 3,0 3,1 Ошибка цитирования Неверный тег <ref>; для сносок Şengör2011 не указан текст
  4. ↑ 4,0 4,1 Ошибка цитирования Неверный тег <ref>; для сносок Drimmel1979 не указан текст
  5. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Gurk1999 не указан текст
  6. ↑ 6,0 6,1 6,2 Ошибка цитирования Неверный тег <ref>; для сносок Ilyashuk2009 не указан текст
  7. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Selverstone2005 не указан текст
  8. ↑ 8,0 8,1 Ошибка цитирования Неверный тег <ref>; для сносок GobetTinner2003 не указан текст
  9. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Janoschek1980 не указан текст
  10. ↑ 10,0 10,1 Ошибка цитирования Неверный тег <ref>; для сносок Hornung2010 не указан текст
  11. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Mählmann1992 не указан текст
  12. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Ratschbacher1991 не указан текст
  13. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Handy1996 не указан текст
  14. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Masini2012 не указан текст
  15. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Gosso2012 не указан текст
  16. ↑ Ошибка цитирования Неверный тег <ref>; для сносок PigazziBersezio2022 не указан текст
  17. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Ferrari2011 не указан текст
  18. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Bernoulli1974 не указан текст
  19. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Ferreiro Mählmann2012 не указан текст
  20. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Sternai2019 не указан текст
  21. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Schlüchter2013 не указан текст
  22. ↑ Ошибка цитирования Неверный тег <ref>; для сносок BertleKiller2003 не указан текст
  23. ↑ Ошибка цитирования Неверный тег <ref>; для сносок LivioFerrario2023 не указан текст
  24. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Wiemer2009 не указан текст
  25. ↑ 25,0 25,1 Ошибка цитирования Неверный тег <ref>; для сносок AlbiniMorelli1994 не указан текст
  26. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MüllerMayerRosa1980 не указан текст
  27. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Agliardi2009 не указан текст
  28. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Fanetti2008 не указан текст
  29. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Ostermann2014 не указан текст
  30. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Schmid2009 не указан текст
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